Commercial and industrial floor maintenance machines such as sweepers and scrubbers incorporate a vacuum system for dust control or for removing liquids such as cleaning solutions from a floor being cleaned. The vacuum system typically includes a radial flow fan having an impeller driven by a motor for creating the vacuum. In a conventional fan the impeller is enclosed within a housing. The housing includes a collector, often of volute shape, around the periphery of the impeller which gathers the exhaust air from the impeller and directs it out through one or more openings in the collector. A diffusion channel may also be provided in the housing, spaced radially between the periphery of the impeller and the collector. While this arrangement performs the desired function, the need for a specially-formed housing incorporating the collector increases the cost of the unit, and use of a collector reduces the airflow for a given power input. Low cost fans have been used that have neither a collector nor a diffuser. While this approach saves on housing costs, it has the disadvantages of lower air flow and higher noise.